Green Garnet Phosphors for Backlighting Wavelength Shift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current garnet-based phosphors, such as YAG:Ce and LAG:Ce, have peak emission wavelengths that are too long for effective use in backlighting applications, necessitating a phosphor with a shorter peak emission wavelength while maintaining high temperature stability and quantum efficiency.
Innovation Solution
Development of green-emitting, garnet-based phosphors with specific chemical formulas, including (Lu1−a−b−cYaTbbAc)3(Al1−dB5(O1−eCe)12:Ce,Eu, where A is Mg, Sr, or Ba, and B is Ga or In, to shift the peak emission wavelength to shorter values, and other variations that allow for excitation by blue light and combination with yellow-green and red phosphors to produce white light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If YAG:Ce or LAG:Ce phosphors are used, then high quantum efficiency and thermal stability are achieved, but the peak emission wavelength is too long for backlighting applications
Solution Approach 1:
The patent changes the chemical composition parameters of the garnet phosphor by substituting Yttrium with Lutetium and introducing alkaline earth metals (Mg, Ca, Sr, Ba) at controlled concentrations. This parameter modification shifts the peak emission wavelength from the red region (YAG:Ce) or yellow-green region (LAG:Ce) to the green region, while maintaining the crystal structure that provides thermal stability and high quantum efficiency
Solution Approach 2:
The patent creates composite phosphor materials by combining multiple elements within the garnet structure - specifically (Y1-aLua)(Al5-bBb)(O1-cDc)12 where B represents alkaline earth metals and D represents halogens. This composite approach allows simultaneous optimization of emission wavelength, thermal stability, and quantum efficiency by leveraging the complementary properties of different elements in the crystal lattice
2Object-generated harmful factors
If the peak emission wavelength is shortened for backlighting applications, then suitability for backlighting improves, but quantum efficiency and thermal stability may deteriorate
Solution Approach 1:
The patent carefully controls the substitution parameters (a, b, c) to achieve the desired wavelength shift while preserving the crystal field environment that enables high quantum efficiency. By limiting alkaline earth metal substitution to specific ranges and compensating with halogen substitution, the patent maintains efficient energy transfer pathways from Ce3+ activators while achieving green emission
Solution Approach 2:
The patent introduces local compositional variations within the garnet structure by substituting specific cation sites with different elements. The alkaline earth metals occupy specific crystallographic sites while halogens substitute oxygen at other sites, creating localized modifications that tune the emission wavelength without disrupting the overall crystal structure and energy transfer mechanisms that ensure high quantum efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The new phosphors exhibit a shorter peak emission wavelength, enhanced photoluminescent intensity, and improved thermal stability, making them suitable for backlighting and white light illumination systems with improved color coordinates and efficiency.
Implementation Method 1
green-emitting, garnet-based phosphors... excitation by blue light... emit light having a peak wavelength ranging from about 480 nm to about 570 nm
Data Source
AI summary
Disclosed herein are green-emitting, garnet-based phosphors having the formula (Lu1−a−b−cYaTbbAc)3(Al1−dBd)5(O1−eCe)12:Ce,Eu, where A is selected from the group consisting of Mg, Sr, Ca, and Ba; B is selected from the group consisting of Ga and In; C is selected from the group consisting of F, Cl, and Br; and 0≤a≤1; 0≤b≤1; 0<c≤0.5; 0≤d≤1; and 0<e≤0.2. These phosphors are distinguished from anything in the art by nature of their inclusion of both an alkaline earth and a halogen. Their peak emission wavelength may lie between about 500 nm and 540 nm; in one embodiment, the phosphor (Lu,Y,A)3Al5(O,F,Cl)12:Eu2+ has an emission at 540 nm. The FWHM of the emission peak lies between 80 nm and 150 nm. The present green garnet phosphors may be combined with a red-emitting, nitride-based phosphor such as CaAlSiN3 to produce white light.